In large stock pot, cover potatoes with water by 2 inches. Add salt and pepper, and bring to boil then reduce to a simmer.
In large skillet, heat the salt pork. Add the onion and saute. When onions are translucent, add to the simmering potatoes.
Add quahogs, quahog juice, and thyme to the potatoes. Simmer for 30 minutes or until potatoes are cooked through.